In various process industries, particularly the chemical process industries, various liquids, gases, or slurries are maintained under vacuum or under pressure, either in vessels or in flow conduits, and the pressure values must be monitored. For this purpose, suitable gages or recording instruments are mounted on the process vessels or on the flow lines or are remotely coupled thereto, to sense, indicate and record the existing pressure values.
In most chemical processes, as well as other process industries, it is both necessary and desirable to isolate the pressure sensing element of the recording instrument from the abrasive or corrosive or clogging action of the process material so that the sensing element will not be subjected to undue deterioration, injury, or wear. To accomplish this isolation, it is a common practice to provide a flange member or similar coupling unit having a cavity in communication with the pressure recording instrument. This instrument flange member is secured in abutting relationship to a process flange member which has a cavity in communication with the pressure fluid to be monitored. A flexible diaphragm of metal, rubber, or synthetic resin serves to partition the instrument cavity from the process fluid cavity and is secured between the coupling or flange members at its marginal positions.
One side of the flexible diaphragm is exposed to the pressure of the process fluids. The cavity in the instrument flange on the other side of the flexible diaphragm is filled with light oil or other suitable hydraulic fluid for communication with the pressure sensing element. The central portion of the flexible diaphragm is displaced or expanded in response to pressure fluctuations from the process fluid cavity and transmits these changing pressure values through the hydraulic fluid medium in the instrument flange cavity for sensing by recording gage or instrument.
All parts of the diaphragm seal that come in contact with a process fluid or gas, in a pressure system, are classified and known as "wetted" parts. The material of the wetted parts must be compatible with and not generally affected by the process fluid or gas. The synthetic resin polymeric material TEFLON is the choice material for a "wetted part" by many in the chemical industry because of the compatibility of TEFLON with practically all corrosive fluids and gasses. It is also the choice of many other industries such as foods, pharmaceuticals, paper pulp, etc.
The design and construction of a flanged-type diaphragm seal requires that an adapter ring must be used to interface properly with a pipe flange that a user would have in his pipeline. At times, the material of the adapter ring will include TEFLON. TEFLON, within the adapter ring, and elsewhere, shows a characteristic that is known as "cold flow". When TEFLON is squeezed, it will act similar to a gob of stiff grease. TEFLON cannot be compressed. When squeezed, TEFLON will flow from the squeezed area to an area that is not confining, or at least less confining. One type of diaphragm seal adapter ring construction utilizes TEFLON that is shaped as a doughnut and used as an insert or liner confined by an outer metal shell or ring at the periphery. This outer metal shell or ring contains the cold flow of the TEFLON. In common parlance, the adapter ring is called a "TEFLON-lined" adapter ring.
A flange-type diaphragm seal is attached to a user's pipe flange, of the same pipe class and pressure class, by bolts that are torqued sufficiently so as to prevent leakage at the attaching faces. Ideally, the amount of torquing is controlled so that the TEFLON will not distort and "cold flow" elsewhere adjacent to the diaphragm itself. The adapter ring is used between the instrument flange space of the diaphragm seal and the face of the user's pipe flange so as to interface the flanges properly.
At present, a TEFLON-lined adapter ring is manufactured by Zavoda Manufacturing Company, Inc., of 8402 Scranton Street, Houston, Tex., and other manufacturers. After experimentation, it has been found that the lines of force that are transmitted by the torquing of the bolts of the instrument flange transmit these forces directly to the metal shell of the adapter ring. The instrument flange also transmits a force on the periphery of the diaphragm. The diaphragm, in turn, exerts the forces to the TEFLON liner of the adapter ring. The force, created by the torquing of the flange bolts, is transmitted through the outer metal adapter ring shell of the adapter ring assembly to the user's pipe flange. A suitable force is required to seal all interfaces between the instrument flange of the diaphragm seal and the user's metal pipe flange.
It is an object of the present invention to provide a TEFLON lined adapter ring that is suitable for attachment to TEFLON lined pipe.
It is another object of the present invention to provide a TEFLON-lined adapter ring that minimizes any effect of thermal expansion and contraction of the TEFLON material.
It is another object of the present invention to provide a TEFLON-lined adapter ring that allows easy attachment and detachment of the diaphragm seal from the pipeline.
It is still a further object of the present invention to provide a TEFLON-lined adapter ring that will not deform or affect the operation of the diaphragm within the diaphragm seal assembly.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.